1. Field of the Invention
This invention relates to downhole testing tools, and more particularly, to a testing apparatus using a hydraulic set packer.
2. Description of the Prior Art
A known method of testing a well formation is to isolate the formation between a pair of inflatable packers with a flow port therebetween adjacent to the formation. The packers are inflated by means of a pump in the testing string which pumps well annulus fluid or mud into the packers to place them in sealing engagement with the well bore. A variety of such pumps is available.
Some downhole pumps are actuated by the vertical reciprocation of the tubing string connected to the pump. Other pumps are operated by rotation of the tubing string relative to the pump structure connected thereto, and one type of rotationally operated pump uses a plurality of vertically reciprocating pistons which are driven by a cam structure. Inlet and outlet valves are positioned adjacent to each of the pistons. Later pumps have a simpler, sleeve-type pump piston.
As mentioned, these pumps may be used to inflate inflatable packers, such as the Halliburton Services Hydroflate.RTM. packer. Such packers are frequently used in applications where there is not enough weight on the tool string sufficient to set other types of packers. Another advantage of inflatable packers is that they are flexible and are well adapted for use in well bores which are considerably larger, relatively, than the tool string. However, inflatable packers generally will not hold as much pressure as a squeeze packer.
In addition to the problem of not having enough weight to set a typical squeeze packer, packers of this type, such as the RTTS packer and Champ.RTM. III packer also manufactured by Halliburton Services, require the use of mechanical slips to grippingly engage the well bore before the packer element may be set.
The hydraulic set packer and testing apparatus of the present invention solves the problems of both inflatable packers and typical squeeze packers. The packer of the present invention is set hydraulically by pumping fluid thereto. This pumping may be done with the same type of pump as for inflatable packers or by pumping from the surface. An advantage is the hydraulic set packer will hold more pressure than a comparable inflatable packer. Also, the packer of the present invention is more cost effective than a typical squeeze packer and does not require any mechanical slips against the well bore.
In addition to drill stem testing, inflatable packers are used in testing blowout preventers. The hydraulic set packer of the present invention may be used to replace such inflatable packers in blowout preventer testing, and again, the hydraulic set packer has the advantage of holding more pressure than the inflatable packer, thereby generally achieving better test results.
Hydraulic packers are known in the art, but have not been used in a well testing string of the type of the present invention. Further, the preferred embodiment of the packer of the present invention has a simple construction utilizing a piston slidably disposed in a piston chamber and wherein a portion of the piston directly engages the packer element during a setting operation.